The association of placenta previa and early preterm birth in pregnancies complicated by placenta accreta spectrum

To determine whether placenta previa in the setting of placenta accreta spectrum (PAS) is significantly associated with early preterm birth (PTB), less than 34 weeks of gestation. This is a single centre study involving a racially diverse cohort of 132 singleton pregnancies complicated by PAS from 2016 to 2020. All patients were managed at a large quaternary hospital with a multidisciplinary accreta team. Participants with available data regarding placental location, maternal age, gestational age at delivery, gravidity, race, type of medical insurance and prior preterm delivery were included. The cohort was identified as those having placenta previa and those with placentation elsewhere. Early PTB (< 34 weeks) was the primary outcome. Measures of association were demonstrated with odds ratios using a 95% confidence interval which were estimated by logistic regression. P < 0.05 is considered statistically significant. The overall early PTB rate for the 132-patient cohort was 28%. The early PTB rate in PAS patients was 31.1% for those with placenta previa and 20.5% for those without previa (p = 0.21). Notably, the presence of placenta previa was not significantly associated with early PTB (OR 1.76, 95% CI: 0.72–4.29). Similarly, maternal age, gravidity, insurance type, race and prior preterm delivery were not associated with early PTB in the presence of PAS. Further analysis revealed that only a prior preterm delivery history (< 37 weeks) was significantly associated with subsequent delivery below 32 weeks among PAS patients (OR 2.55, 95% CI: 1.01- 6.46, p < 0.05). Although our overall rate of preterm delivery was higher in the previa group, there was no significant association between placenta previa and early PTB among PAS patients. Only a prior preterm delivery history was significantly associated with preterm delivery less than 32 weeks in pregnancies complicated by PAS. The findings may assist providers in counselling patients regarding preterm delivery among PAS patients.